1. Technical Field
The present invention relates to a liquid crystal display device and a method of driving it, and in particular relates to a black insertion drive method for improving a moving image performance.
2. Related Art
In a case of classifying displays particularly from a viewpoint of a moving image displays, they are divided broadly into an impulse response type display and a hold response type display. The impulse response type display is a type in which, as in a decay characteristic of a cathode-ray tube, a luminance response is reduced immediately after a scanning, and the hold response type display is a type which, as in a liquid crystal display device, continues to maintain a luminance based on display data until a next scanning.
As a feature of the hold response type display, in a case of a still image, it is possible to acquire a good display quality having no flicker but, in a case of a moving image, there is a problem in that a so-called moving image blurring occurs in which a perimeter of a moving object looks blurry, reducing a display quality significantly.
A cause of the occurrence of the moving image blurring lies in a so-called retinal afterimage formed by an observer, when moving a line of sight along with a movement of an object, interpolating a display image before and after the movement with respect to a display image whose luminance is maintained, meaning that the moving image blurring is not completely eliminated no matter how greatly a response speed of the display is increased.
In order to solve this problem, a method is effective in which, in one frame, a regular video and a black image are displayed in a certain proportion (hereafter called a black insertion drive method) and, by once cancelling the retinal afterimage, the impulse response type display is approximated (refer to a patent document 1, to be mentioned below).
FIG. 8 is a diagram for illustrating an outline of one example of a heretofore known black insertion drive method.
The method shown in FIG. 8 is one arranged in such a way that, as shown in DSCN of FIG. 8, in one frame FLAM, from a top of a display panel downward, a video voltage is written sequentially into pixels on one display line, also, as shown in BSCN of FIG. 8, a black image voltage is written sequentially into pixels on one display line, and the writing of the video voltage shown in DSCN of FIG. 8 and the writing of the black image voltage shown in BSCN of FIG. 8 are alternately carried out.
That is, in FIG. 8, a step 1 of writing a black image voltage after a period TD (hereafter called a video display period) has elapsed after writing a video voltage into pixels, and a step 2 of writing a video voltage after a period TB (hereafter called a black image display period) has elapsed after writing the black image voltage, are repeated. In FIG. 8, PV indicates a display line position of a liquid crystal display panel, and T a time.
As a related art document relating to the invention, there is a patent document 1 JP-A-2001-60078.